Data collected on 948 women whose first pregnancies were either carried to term or terminated by legal abortions are being studied to determine relationships between abortions and future pregnancies. A Markov Chain model, a statistical technique which treats data in chronological fashion in order to test whether certain biological factors are dependent on other biological happenings, is fitted to the data. As an example of its use, the chain might represent the dependence of a premature birth on an induced abortion of an earlier pregnancy. We hope to provide a description of these interrelationships, a tool for prediction and answers to some questions concerning the risks of abortions. The Markov Chain has been used in theoretical fertility studies and in other biomedical problem studies, but this is the first time it will test field data with a large, complex model. The data collection and initial analysis of this research were funded with an award to Dr. Hogue from the Ford and Rockefeller Foundations Program in Support of Social Science and Legal Research in Population Policy.